London, England March 31, 1939

On this date in 1939, two weeks after German troops entered Prague and all of Czecho­slo­va­kia fell under the German boot, the British govern­ment, followed a few days later by the French, pledged to guar­an­tee the inde­pen­dence (though inter­estingly not the terri­torial integ­rity) of Poland. “If any action clearly threatened Polish inde­pen­dence,” the British secu­rity guaran­tee read, “and if the Poles felt it vital to resist such action by force, Britain would come to their aid.” A week later, when Polish Foreign Minis­ter Józef Beck visited London, Britain and Poland agreed to begin talks with the inten­tion of formal­izing a mili­tary alli­ance. The idea of an alli­ance, which had broad public support, was a sym­bolic line in the sand drawn by Britain and France, both nations viewing Poland as the next target of Adolf Hitler’s seemingly bound­less aggres­sion. Stepping over that line would have con­se­quences. (It goes almost with­out saying that the Anglo-French security guar­an­tee of March and April 1939 was unenforce­able with­out assistance from Poland’s eastern neighbor, the Soviet Union.)

That the Western democracies would guarantee Poland’s inde­pen­dence so enraged Hitler that he told com­man­ders of his Wehr­macht (German armed forces) to begin stra­tegic plan­ning for Fall Weiss (Oper­a­tion White), the destruc­tion of Poland, with a pro­vi­sional start date of Septem­ber 1, 1939. A defeated Poland would elim­i­nate the “Free City of Danzig” (German, Freie Stadt Danzig), con­sisting of the Bal­tic sea­port of Dan­zig (today’s Gdańsk) and sur­rounding areas, which were roughly 95 per­cent ethnic German. This geo­graphi­cal oddity of the 1919 Ver­sailles Peace Treaty was admin­is­tered by a League of Nations high com­mis­sioner (at the time, a Swiss), and most Germans found Danzig’s exis­tence a vexa­tion because it and the so-called Polish Corri­dor east of Danzig split East Prus­sia from West Prus­sia and the rest of Nazi Ger­many (see map). Ger­man units were to in­vade Poland from three direc­tions: the main attack from Germany across the west­ern Polish border, a second route from the East Prus­sian enclave, and a third attack by German and allied Slo­vak units from the Czech puppet state (since March 14, 1939) of Slo­va­kia. All three assaults were to con­verge on Warsaw, the Polish capital.

Fall Weiss was the first European military oper­a­tion of World War II. It would be six years of bru­tal occu­pa­tion and the death of four mil­lion Polish civil­ians, three-quarters of them Jews who died in con­cen­tra­tion camps or gas cham­bers, before the last units of the Wehr­macht were swept from Polish soil. As for Danzig itself, many of its resi­dents perished or fled west­ward ahead of the Soviet on­slaught and the city’s destruc­tion and con­quest by the Red Army in March 1945. After the war most of the remaining ethnic Germans were forcibly expelled. The city was sub­se­quently placed under Polish admin­is­tra­tion by the Allied Pots­dam Agree­ment (August 1, 1945), and Poles from Central and Soviet-an­nexed Eastern Poland were brought in to replace the German population.

German Conquest of Poland, September 1 to October 6, 1939

Map of Danzig (Gdańsk), 1939

Above: Map of Danzig (“Free City of Danzig,” present-day Gdańsk) and Poland’s corri­dor to the Baltic Sea (“Polish Corri­dor”) squeezed between German West and East Prus­sia on the eve of war, 1939. The Memel Terri­tory (today’s Kalinin­grad Oblast) was retrans­ferred by an intim­i­dated Lithu­ania to Nazi Ger­many on March 23, 1939. This event proved to be the last of a series of blood­less annex­a­tions of terri­tories sep­a­rated from Germany by the 1919 Treaty of Versailles.

Germany invades Poland: German troops remove Polish insignia near Sopot, Poland, 1939Germany invades Poland: German and Slovak soldiers in Southeastern Poland, 1939

Left: German troops remove Polish insignia at the Polish-Danzig border near Sopot (German, Zoppot), September 1, 1939.

Right: German and Slovak soldiers pose with civilians in Komańcza, Southeastern Poland, September 1939.

Germany invades Poland: German cavalry and motorized units, Poland 1939Germany invades Poland: Royal Castle in Warsaw burning, 1939

Left: German cavalry and motorized units enter Poland from East Prussia, 1939.

Right: The Polish Royal Castle in Warsaw on fire after being shelled by Germans, Septem­ber 17, 1939. On Septem­ber 26 German troops captured three key forts defending Warsaw and entered the capital the next day.

English Language German Propaganda Film: “Liberation” of Danzig and Wehrmacht’s Assault of Poland, September 1939 (Skip first minute)